The field of the invention is illuminated information displays, and more particularly, operator displays for electrical controls.
For certain applications and in certain countries, switches which are actuable or releasable by a twisting motion are preferred or required. Such switches can be incorporated into a control circuit to be either push-on and twist-off or push-off and twist-on. The pushbutton operators of these switches can be made of a transparent plastic material and a lamp can be provided behind the operator to illuminate the operator in either its extended or its retracted position, or in both positions. A switch of this type is fully described in Baran et al U.S. Pat. No. 4,404,445 issued Sept. 13, 1983.
One problem with such twist type switches is that the switch operating personnel must be informed of the direction of rotation of the switch operator in order to either actuate or to release the switch. This is especially important when the switch must be twisted to either energize or de-energize a circuit in an emergency situation. Some indicator must therefore be provided on the switch or on the control panel to inform the operating personnel which direction to turn the operator to manipulate the switch.
Such an indicator could be provided as a printed instruction or as a label on the control panel. One problem with providing the instruction on the control panel is that the switches may be sold separately and assembled to the control panel in the field. Field assembly personnel would therefore be required to affix the instruction to the control panel properly and in a location proximate to the switch so that it would be readily visible by the operating personnel. Of course, this introduces a chance for error into the installation of a twist type switch which should be avoided.
Another solution to providing instructions on how to operate a switch would be to apply a printed instruction or a label directly to the switch. A problem with this solution is that these switches can be subjected to harsh environments where solvents and hard use can eradicate printed matter or destroy a label. Also, this solution requires an extra operation in manufacturing to apply the instruction.
Yet another solution to providing instructions on how to operate a switch would be to mold or engrave the instructions into the operator portion of the switch. Engraved or molded instructions are more durable than printed instructions so that this would be one way to overcome the problem outlined in the previous paragraph. However, molded or engraved instructions would be the same color as the operator portion and would therefore not be highly visible as required of instructions for such control switches. Therefore, it can be appreciated that a need exists for an improved means for clearly and durably displaying instructions for electrical controls and particularly, for twist type electrical switches.